Although magnesium deficiency is common, it rarely results in yield reduction. However, its presence might offer entry points for botrytic and other diseases. The deficiency usually exists only in the plant, not in the soil, and is related to high-potassium feeds or poor root development. Both these make it difficult for the plant to take in sufficient magnesium, thereby forcing the plant to move magnesium from the old leaves to the new. Magnesium, being a vital part of chlorophyll, is easy to monitor because its absence is made obvious by the absence of chlorophyll. A magnesium deficiency is easily corrected with Epsom Salts, in a 2% solution spray. In fact, some growers provide most of the magnesium requirements of a crop in frequent sprays.


Calcium deficiency is usually expressed as blossom-end rot of the fruit and as dieback of the growing tips. In most cases the calcium deficiency is not in the soil but is induced. The most likely cause is water stress on the plant resulting from inadequate or uneven watering, frequent and large variations in relative humidity, or a high level of salts. Sprays of calcium nitrate or calcium chloride, in a 2% solution, help correct a calcium deficiency, but improving the water balance in the plant is a more practical solution to the problem.

Calcium, magnesium, and potassium are believed to compete with each other, with a varying degree of success, for the same sites of absorption by the plant; it is useful to remember that increasing one of them affects the other two.


This element is rarely a problem because it is present in many fertilizers as a carrying element and because it is a commonplace pollutant. However, high sulfur levels can become sources of excessively high salts and could also be detrimental to the uptake of molybdenum.


Iron deficiency, a frequent problem, is usually expressed in chlorotic young leaves. Similar to calcium deficiency, iron deficiency is, in most cases, induced. Indirect causes of iron deficiency may be soil pH that is too high, a manganese level that is too high, and poor root growth or poor anaerobic soil conditions resulting from overwatering. In many cases, improved soil aeration or drying out the soil or peat corrects the problems. Soil applications and foliar sprays of iron salts or iron chelates are helpful, but as usual the most recommended action is the elimination of the source of the problem.


Manganese deficiency is frequently confused with iron deficiency and is often an expression of iron toxicity. Manganese toxicity is a more serious problem, encountered when steaming is not well controlled and is not followed by leaching.


Peat media may occasionally be deficient in copper, but the widespread use of copper plumbing ensures an adequate copper supply in most cases.


Boron deficiency is expressed as brittleness of leaves, premature wilting, and, in acute form, as dieback of the growing tips. This deficiency can be corrected easily with foliar sprays of a Borax solution, but the rate of application must be monitored carefully because boron toxicity can cause severe plant damage.


This element is rarely in deficiency. Toxicity is a potential problem in recirculating hydroponic systems, as there is always some zinc released from galvanized pipes.


A molybdenum deficiency can be induced by acid soil conditions or high sulfur levels. Although symptoms of molybdenum deficiency are not easily distinguishable, leaf tissue analysis is a dependable diagnostic tool.

Chapter 4. General cultural practices Crop scheduling

Early spring tomatoes

  • Sow seed 25 October-25 November
  • Set plants in permanent bed 1 January-15 January
  • Harvest April to July
  • Remove plants 1 July-20 July
  • Sterilize soil 1 July-25 July

Fall tomatoes

  • Sow seed 15 June-15 July
  • Set plants in permanent bed 20 July-15 August
  • Harvest October to December
  • Remove plants 15 December-l January
  • Sterilize soil 16 December-l January

The early-spring tomato crop is usually replaced by a late-spring tomato crop in old single plastic houses where light transmission is poor and heating costs are high.

Late-spring tomatoes

  • Sow seed 15 December-15 January . Set plants in permanent bed 1 February-1 March
  • Harvest May to July
  • Remove crop 20 July-25 July

Sometimes the spring crop of tomatoes is extended to the following November if plants are healthy. The replacement of the spring crop of tomatoes by a spring crop of cucumbers and the fall crop of tomatoes by a fall crop of cucumbers or two fall crops of lettuce are variations to the standard scheduling of one spring and one fall crop of tomatoes per year.

Growing Soilless

Growing Soilless

This is an easy-to-follow, step-by-step guide to growing organic, healthy vegetable, herbs and house plants without soil. Clearly illustrated with black and white line drawings, the book covers every aspect of home hydroponic gardening.

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